Senators unwilling or unable to provide documented proof of their residence are being called on the carpet and forced to explain themselves in a series of meetings with members of the Senate's internal economy committee, CBC News has learned.

Those meetings begin today. It's unclear how many or which senators will be called.

Conservative senators David Tkachuk and Carolyn Stewart Olsen will play the role of interrogator, along with Liberal Percy Downe, the CBC's James Cudmore reported.

The internal economy committee asked all senators last December to prove where they live through drivers licences, health cards and tax filings. The committee is in charge of senators' budgets and administrative matters.

Nothing to be shortcircuited

Senator Mike Duffy said Friday he would repay expenses claimed for his home in Ottawa, explaining he made a mistake in declaring that his primary residence was in Prince Edward Island. Other senators, including Pamela Wallin, Mac Harb, Dennis Patterson and Patrick Brazeau, have faced questions about their expense claims and residency declarations.

Cowan said Monday that paying back the expenses may not be enough, depending on the results of the audit.

"That's not necessarily the end of it, absolutely not. It may be, but it depends on what the audit report says," Cowan said.

Emphasizing that he can't speak for any senator but himself, Cowan said he finds the form filled out by senators to be perfectly clear. If there is something confusing about a form he's filling out, he says, "You ask about it. That's what I do when I don't understand something. I never sign anything that I don't understand."

Cowan says he and LeBreton agree on how the issue of senator expenses should be handled, regardless of party.

"I don't think there's any difference between Senator LeBreton and me on this. We are both determined that this is dealt with fairly, openly, transparently, and nothing's going to be swept under the carpet. Nothing's going to be shortcircuited."

'Unacceptable for any other Canadian'

NDP Leader Tom Mulcair pointed to Duffy's claim that the form senators have to fill out is unclear, and to the fact Wallin has an Ontario health card but tells the Senate she resides in Saskatchewan.

"He says the form is too complicated …She told the federal government that she lived in one province while telling a provincial government that she lived in another. This would be unacceptable for any other Canadian. Why does the prime minister seem to think it's acceptable for his Conservative senators?" Mulcair said.

NDP ethics critic Charlie Angus said EI forms tell applicants that if they misrepresent the facts to make a false claim, they are committing fraud and could be prosecuted.

"So will the government hold senators who break the rules to the same standards they hold unemployed Canadians to?" Angus said.

Government House Leader Peter Van Loan says the government has committed to ensuring expenses and the rules governing them are appropriate, and to reporting publicly about them.

"Senators Patterson, Wallin and Duffy all own property in the provinces and territory they represent. They maintain deep and continuing ties to those regions and in fact three senators all spend considerable time in their home provinces and territory," he said.

"The reality is if you want to see real change in the Senate, if you want to see real change towards an accountable Senate, you need to embrace the Conservative proposal to actually let Canadians have a say who represents them in the Senate. The NDP simply won't do that."